In this series of studies we wish to investigate both the short and long term pathologic and physiologic effects of ionizing radiation on the liver, in order to develop a rational and efficient approach to treatment of upper abdominal cancers without sacrificing either a liver function or cancericidal effect. During the last ten years the previous concept that the liver was relatively radio resistant has changed, since recent data have shown that it is actually the opposite situation: the liver is really quite a radio-sensitive organ. The specific objectives of our study include: l. To define the effect of different time-dose- fraction combinations on whole and partial liver irradiation, as occurs during treatment of upper abdominal cancers. 2. To manipulate time- dose, fractionation and liver volume, as well as certain chemicals in an attempt to prevent or reverse the injury. 3. To attempt to correlate the different functional and radio isotopic technics of liver evaluation with the histopathologic and electron microscopic changes. 4. To develop and study the chronic effects of irradiation to the liver as a possible model of chronic liver disease, portal hypertension, and ascites. Screened, dewormed, vaccinated, quarantined dogs will be anesthesized and irradiation given to the liver. Phase I: To develop an LD80 model. Phase II: To manipulate time, dose and fractionation in whole liver irradiation. Phase III: To vary the liver volume irradiation (25-90%) and to give heparin to certain sub-groups. Parameters (pre-treatment and at 3-4 mo. intervals): physical exam., esophagoscopy, laparotomy, liver biopsy, portal manometry, liver scanning, liver functions. Analysis: either parametric or non- parametric-ANOVA and correlation tests.